TY - JOUR
T1 - Nanostructure, electrochemistry and potential-dependent lubricity of the catanionic surface-active ionic liquid [P6,6,6,14] [AOT]
AU - Zhang, Yunxiao
AU - Marlow, Joshua B.
AU - Millar, Wade
AU - Aman, Zachary M.
AU - Silvester, Debbie S.
AU - Warr, Gregory G.
AU - Atkin, Rob
AU - Li, Hua
PY - 2022/2/15
Y1 - 2022/2/15
N2 - Hypothesis: A catanionic surface-active ionic liquid (SAIL) trihexyltetradecylphosphonium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate ([P6,6,6,14] [AOT]) is nanostructured in the bulk and at the interface. The interfacial nanostructure and lubricity may be changed by applying a potential. Experiments: The bulk structure and viscosity have been investigated using small angle X-ray scattering (SAXS) and rheometry. The interfacial structure and lubricity as a function of potential have been investigated using atomic force microscopy (AFM). The electrochemistry has been investigated using cyclic voltammetry. Findings: [P6,6,6,14] [AOT] shows sponge-like bulk nanostructure with distinct interdigitation of cation–anion alkyl chains. Shear-thinning occurs at 293 K and below, but becomes less obvious on heating up to 313 K. Voltammetric analysis reveals that the electrochemical window of [P6,6,6,14] [AOT] on a gold micro disk electrode exceeds the potential range of the AFM experiments and that negligible redox activity occurs in this range. The interfacial layered structure of [P6,6,6,14] [AOT] is weaker than conventional ILs and SAILs, whereas lubricity is better, confirming the inverse correlation between the near-surface structure and lubricity. The adhesive forces of [P6,6,6,14] [AOT] are lower at −1.0 V than at open circuit potential and +1.0 V, likely due to reduced electrostatic interactions caused by shielding of charge centres via long alkyl chains.
AB - Hypothesis: A catanionic surface-active ionic liquid (SAIL) trihexyltetradecylphosphonium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate ([P6,6,6,14] [AOT]) is nanostructured in the bulk and at the interface. The interfacial nanostructure and lubricity may be changed by applying a potential. Experiments: The bulk structure and viscosity have been investigated using small angle X-ray scattering (SAXS) and rheometry. The interfacial structure and lubricity as a function of potential have been investigated using atomic force microscopy (AFM). The electrochemistry has been investigated using cyclic voltammetry. Findings: [P6,6,6,14] [AOT] shows sponge-like bulk nanostructure with distinct interdigitation of cation–anion alkyl chains. Shear-thinning occurs at 293 K and below, but becomes less obvious on heating up to 313 K. Voltammetric analysis reveals that the electrochemical window of [P6,6,6,14] [AOT] on a gold micro disk electrode exceeds the potential range of the AFM experiments and that negligible redox activity occurs in this range. The interfacial layered structure of [P6,6,6,14] [AOT] is weaker than conventional ILs and SAILs, whereas lubricity is better, confirming the inverse correlation between the near-surface structure and lubricity. The adhesive forces of [P6,6,6,14] [AOT] are lower at −1.0 V than at open circuit potential and +1.0 V, likely due to reduced electrostatic interactions caused by shielding of charge centres via long alkyl chains.
KW - Atomic force microscopy
KW - Cyclic voltammetry
KW - Friction
KW - Nanostructure
KW - Rheology
KW - Surface-active ionic liquid
UR - http://www.scopus.com/inward/record.url?scp=85118539494&partnerID=8YFLogxK
U2 - 10.1016/j.jcis.2021.10.120
DO - 10.1016/j.jcis.2021.10.120
M3 - Article
C2 - 34752982
AN - SCOPUS:85118539494
VL - 608
SP - 2120
EP - 2130
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
SN - 0021-9797
IS - Part 2
ER -